Last chance for ocean swim as temp drops

For those thinking of visiting the beach, the long weekend looks like the last chance before much colder waters arrive.

As many coast dwellers will know, the waters off the South Coast have been unseasonably warm for this late in the year – much as air temperatures have tracked well above average since March.

"It's ridiculously warm," said Bill Burgess, a Bondi Iceberger who has been swimming through winter for the past quarter-century. "You don't need a cap."

While water temperatures around almost all of Australia have been well above normal for the past three years, the biggest anomaly lately has been off the Sydney coast.

The present temperatures of 20 to 21 degrees are a couple of degrees warmer than usual for the region and higher than during some periods of February, said David Griffin, an oceanographer with the CSIRO.

“There's been an extended period of extremely warm water,” Dr Griffin said.

Spurring the urgency of a late-season beach visit is a large "cold-core eddy" that is about to break up Sydney's balmy coastal conditions. 

The large body of cold water has been edging westwards for some weeks from the Tasman Sea and is beginning to mix in and break up the warm currents flowing south along the coast, Dr Griffin said.

The warm surf "may be about to return to normal conditions so enjoy it while it lasts", he said.

Deterring beachgoers, though, may be the mixed outlook over the three-day break. 

Air temperatures are likely to remain moderate in the city with maximums of 19 to 20 degrees, with the chance of showers and even fog in the west each day.

Morning dips may also be less pleasant with minimums of 11 to 12 degrees expected. While typical for June for Sydney, those minimums will seem chilly compared with the 17 to 18 degrees experienced on Friday morning.

Thursday night's minimum of 17 degrees wasn't that far off the record high minimum of 18.4 degrees set in 1873, according to the weather bureau.

Mr Burgess, 70, said he'll keep swimming even if sea temperatures sink towards the normal winter low of about 16 to 17 degrees over coming days.

Luke Daniels, a lifeguard for six years at Bondi Beach, said the beach continued to be "pretty busy", although conditions often remained mild into winter.

Still, this weekend may be the time to take a final dip before spring. "This is the last good bit of warm water," he said.

Most of Australia has seen sea temperatures well above normal for years.

During autumn, for instance, sea-surface temperatures around all of Tasmania, most of Victoria and westward towards the Great Australian Bight were the highest for that season in records going back to 1900, according to satellite data used by the Bureau of Meteorology.

That departure from long-term averages is one reason why the bureau last month adopted a dynamic model for its seasonal forecasting rather than base predictions on long-standing historical records.

Climatologists also say the rising sea temperatures represent a clear signal that the climate is warming – even after stripping out natural variability.

Those warm conditions off southern Australia probably won't prompt too many Victorians and Tasmanians to head for the beach even with mild conditions forecast for the long weekend.

Melbourne, for instance, has recorded its wettest first week of winter in 159 years of records. The city's rainfall tally of 72.8 millimetres – about six times the average – has probably put paid to thoughts of beach towels and togs.

Sydney Morning Herald

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